1. Field of Invention
This invention relates to accessing image information. More particularly, this invention is directed to a system and method for accessing image information by efficiently processing segmentation tags.
2. Description of Related Art
In many current image processing applications, such as digital copying and the like, it is desirable to store image information about the image, in addition to the actual image data that defines the image, on a pixel-by-pixel basis. For example, a single image may contain various types of image data, such as text data, picture data in the form of sampled image data, continuous tone data and/or halftone data, graphics data, such as line art data and the like, and/or background data. It is often useful to store information identifying the data type of the image data for each pixel.
For example, in compressing the image data of such an image, it is often desirable to process the different types of image data using different compression techniques. Background data and continuous tone (contone) image portions that are formed by sampled data, continuous tone data and/or halftone data, for example, do not normally need to be compressed with the same degree of precision as text or line art data. Therefore, a lossy compression technique may be used to process the less loss-critical data, such as the continuous tone or background data, while a lossless compression technique may be used for the text data or line art data.
Accordingly, each pixel of the image is assigned one or more segmentation tags, where each tag identifies a certain type of information about the image data of that pixel. These segmentation tags can be used to represent a segmented image, where all pixels sharing a common set of tag values may be considered a single object.
In prior methods of accessing tag information, all users using tag information had to agree in advance upon what each tag would mean. Reaching such an agreement was logistically problematic, especially when a large number of users were involved. Moreover, even after a set of tags was successfully established, individual users could not freely add new tags as new tags became necessary. Furthermore, procedure calls were typically required to access the segmentation tags of each pixel of an image, resulting in a great deal of tedium in programming and reduced efficiency in accessing the segmentation tags.
Accordingly, in order to obtain maximum benefit of segmentation tags, a system and method for quickly and efficiently accessing tag information is desirable so that image processing apparatus can quickly process and/or reproduce image data, and so that software developers and/or technicians who program the image processing apparatus can do so quickly and efficiently.
This invention provides a system and method for quickly and efficiently processing segmentation tags using lookup tables and bit operations.
In one aspect of the invention, families of segmentation tags are defined so that each pixel of an image may be associated with more than one segmentation tag.
In another aspect of the invention, a lookup table is automatically created based on information contained within header information of an image, and the segmentation tags are accessed using the lookup table and bit operations.
In certain embodiments, the set of allowed tags and/or tag encoding information may be read directly from the image header of the image. In other embodiments, the set of allowed tags and/or the tag encoding information may be read from a separate file.
In another aspect of the invention, a software developer""s tool kit is provided that includes a library that initializes table lookups based on information indicating a set of allowed tags and information indicating how tags are encoded within an image. The library defines at least one macro that provides access to tag information by performing table lookups and bit operations. Using this tool kit, a software developer can easily and quickly access desired tag information while developing software for a digital image output device.
In yet another aspect of the invention, a digital image processing device is provided that includes a segmenter that segments an image by analyzing received image data, associating at least one segmentation tag (which may be a xe2x80x9cNO TAGxe2x80x9d tag) with each pixel of the image data, generating header information and associating the header information with the received image data, and storing the image data along with the segmentation tags and header information. The digital image processing device also includes apparatus capable of performing a minimal set of bit operations, including bit shifts, bits masks and table lookups, and an access library that obtains information indicating the set of allowed segmentation tags and information indicating how the segmentation tags are coded. The access library creates a lookup table based on the obtained segmentation tag information. The digital image processing device accesses at least a portion of the segmentation tag information using the lookup table and the minimal set of bit operations and processes the image data in accordance with the accessed tag information. The digital image processing device further includes an image file sink to which the processed data is output.
These and other features and advantages of this invention are described in or are apparent from the following detailed description of preferred embodiments.